The basic purpose of this research is to examine central nervous system disease tissue for the presence of viral nucleic acids. Nucleic acid hybridization will be used to assay for the presence of viral nucleic acid in the diseased tissue. An important part of this research is the development of an extremely sensitive viral detection test. Very high specific radioactivity viral nucleic acid probe will be necessary for the development of this test. A new method of hybridization which allows a great increase in viral detection sensitivity will also be devleoped.